Carbide Drills
How to Choose 3D, 5D, and 8D Carbide Drills
Understand drill length ratios and how hole depth, rigidity, and coolant affect carbide drill selection.
5/3/2026•By CAGO technical team
Drills Carbide Holemaking
3D, 5D, and 8D describe drill depth relative to diameter. Deeper holes need better rigidity, chip evacuation, and coolant delivery.
- 3D is suitable for shallow general holes.
- 5D covers many medium-depth production jobs.
- 8D needs careful runout control and coolant management.